German Signal Question

Can anyone tell me what the "F" placed on the small boxes along the german railroads mean ?

 

I'm not sure if it might be a Signal Telephone
Post a picture and somebody will know

Or see if you spot one in this video and quote the time

 

Right, these ones, maybe it's as you said just a telephone:

 

Yes, a Telephone cabinet to speak to the signaller.
Along with those near signals I believe they were also placed next to the track where on sections where a big gap between signals existed and it would enable staff to contact the signallers as required.